PHONON ANOMALY IN RAMAN ACTIVE PHONONS OF CUPRATES IN NORMAL STATE

Abstract

We present here a microscopic theory to explain phonon anomaly in Raman active phonons of the cuprates R 2-x M x CuO 4 in normal state. We used electronic Hamiltonion of Fulde in presence of antiferromagnetism. We incorporated phonon interaction to the hybridisation between the conduction electrons of the system and the f-electrons. The spectral density is calculated by the Green fuction technique of Zubarev type at zero wave vector and low temperature limit. Temperature dependence of Raman active phonon frequencies are studied numerically to discern phonon anomalies by varying model parameters like position of f-level (∊f), the effective electron–phonon coupling strength (g), the staggered magnetic field (h) and the hybridisation parameter (V). The phonon anomalies are explained on the basis of softening, hardening and temperature dependence of different Raman modes.